A typical medical droplet as dispensed by an eye dropper bottle can vary, depending on the viscosity and surface tension of the fluid. In order to control the amount of active ingredient that is administered in a single droplet, the concentration of the active ingredient is adjusted by volume. Once the concentration is defined, a correct dosage may require one drop or more. However, since the human eye can typically retain only 7 μl of fluid at a time, even a single medical droplet can result in overflow and loss of part of the medication from the eye. Multiple drop dosage often compounds the problem of medication retention in the eye. Subjects will typically administer all droplets required for a dosage in one sitting, which exacerbates the problem and can result in 50 to 90% of the medication overflowing and leaking out of the eye.
Another further problem is that a single droplet of the defined concentration marks the lower limit of a dose and, as such, the amount of active ingredient that can be administered at the defined concentration. For example, pediatric application where lower doses are often advisable are an illustration of where the size/dose of a droplet can be problematic.
Given the above and other limitations of current ophthalmic delivery, a need exists for an efficient delivery system for solutions to the eye, including solutions containing medicaments.